Modelling of Polypyrrole Actuators
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0889-W05-03.1
Modelling of Polypyrrole Actuators Mehrdad Bahrami Samani1,2, Philip G. Whitten1,2, Geoffrey M. Spinks1,2 and Christopher D. Cook2 1 ARC Centre of Excellence in Electromaterials Science and Intelligent Polymer Research Institute, University of Wollongong, Northfields Ave, Wollongong, NSW, 2522, Australia. 2 Faculty of Engineering, University of Wollongong, Northfields Ave, Wollongong, NSW, 2522, Australia. ABSTRACT Conducting polymers (CP) are a promising area in the field of micro actuators, and have potential applications in micro robotics. Their properties are modelled as having an electro-chemical active component and a passive viscoelastic component. Methods exist to model the passive component as a configuration of springs and dashpots and the electroactive effects as a strain generator. Typically, the strain is assumed to be proportional to the charge transferred, and the two components are assumed to be independent. We show that there is a significant interaction between the two components for polypyrrole actuators, by observing the dynamic elastic modulus whilst varying the electric potential. The elastic modulus was measured in-situ by applying a high frequency rectangular isotonic stress input and recording the corresponding strain output. Two separate potential control inputs, vs. a reference electrode, were used. In the first experiment, a triangular voltage signal with variable frequency was applied to the PPy helix tube actuator and in the second experiment; a step voltage signal was applied to the actuator. The value of total real modulus was calculated during both experiments to evaluate the effect of actuation on the mechanical properties of PPy actuator. The performance of the mentioned method was confirmed by comparing its results to that of a sinusoidal stress input during a temperature ramp through the glass transition of polyethylene terephthalate (PET). We show that polypyrrole actuators show a complex change in stiffness with contractile state, which mimic skeletal muscle [1]. INTRODUCTION The demand for high strain actuators with at least one dimension on the micrometer scale is growing with the development of micro robotics. Conventional rotary motors, pneumatic or electromagnetic actuators are not suitable for many applications. There exists a group of solid-state actuators, materials, which undergo a dimensional change in response to an external stimulus that are starting to be used in many applications. The most common solid state actuators include conducting polymers (CP), shape memory alloys, piezoelectric polymers, and electro active gels [2, 3]. CP are attractive because of the low heat generated during actuation, fast reversible response time, low applied potential and their relatively large strain [1]. By applying a potential, CP actuators are oxidised or reduced within an electrochemical cell. Ion and solvent transport accompany the oxidation or reduction resulting in a volume change. Polypyrrole (PPy) is the most widely researched
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conducting polym
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